olyrx7

Just wondering if the 5 speed rx8 transmissions can take more power then the 6 speed. I saw a few folks ditching the 6speed and going with the jdm/uk ones but just want to confirm power capability As i cant find the threads......

Thank you

RIWWP

iTrader: (2)

The engine will break before either the 6 speed or the 5 speed, so the power limits of each have not been tested for the RX-8. If you are putting a different engine in the RX-8, then chances are you are also putting in a different transmission.

The only 6 speed failure problems due to performance reasons (and not just old age or abuse) has been on RX-8s in the 220whp range, and as far as I am aware, all on a race track in a race and slamming the gears hard. Almost always 4th gear is what goes.

The 5 speed vs 6 speed changes are a carryover from when the NB Miatas were breaking 6 speeds and people were swapping to 5 speeds, and since the NC Miata and the RX-8 share transmission designs, people assume that changing to a 5 speed in an RX-8 would mean a stronger transmission result. However, the NC's 5speed vs 6speed hasn't yielded any strength problems even in the Miata community. The RX-8/NC 6-speed is not at all the same as the NB Miata's 6-speed.

My recommendation: Stick with the transmission you have, unless you have a different gearing preference, or you have a broken 6 speed and only 5 speeds on hand. It can take the power you throw at it. The engine will blow before the transmission does.

olyrx7

I just picked up a turbo charged renesis and the tranny is making noise and I am looking at options.....I have access to a 2011 5 speed and im wondering if it would be better suited to the power?

RIWWP

iTrader: (2)

Sure, pick whichever one you want. Both can hold up to more power than the engine can. The transmission isn't failing because of the power. It would be failing because of abuse or neglect or simple old age.

drum-beats

I agree with RIWWP,
I have a turbocharged RX-8 running around 8psi, I completely destroyed my 5-speed transmission by abusing it on track by drifting,
Brettus has the exact same transmission and has run up to 20psi with no problems at all,
The transmission will last if you treat it right and don't abuse it,

dannobre

iTrader: (3)

The 5 speed is basically the same box that was in the FD RX-7....and it will take more power than the 6 speed RX-8

Brettus

iTrader: (2)

That's why I fitted mine . But I don't tend to destroy transmissions ...........due to not being a maniac .

olyrx7

Thats what I wanted to confirm, thank you

dannobre

iTrader: (3)

LOL....I did well with the 6 speed..it handled a lot of track time.

It died when I went with full slicks and forgot to turn down the boost controller to stay at about 350 ft/lbs torque

4th gear exploded going up a hill...straight torque load...wasn't even a missed shift or anything